The labor task force representing Consolidated Rail Corp.'s 35,000 employes will meet here later this month with prospective Conrail buyers to decide which it will endorse to buy the federally owned railroad.

Brian Freeman, the employes' financial adviser, said the three bidding finalists chosen by the Transportation Department and Conrail's management, which is seeking to purchase the railroad through a public stock offering, have been invited. The meetings are to be held Jan. 22-25, he said.

Employe support is expected to carry considerable weight with Transportation Secretary Elizabeth Hanford Dole, because labor backing will be needed on Capitol Hill when Dole seeks legislation to denationalize the Northeast/Midwest freight railroad.

Dole has been pushing her staff to conclude its study of the bidders so that she can make her decision. A senior department official said the final decision will not be made until labor has expressed its preference. "We'd like to know what they think, and we're in close touch," the official said.

Norfolk Southern Corp., a railroad holding company that operates the second largest system east of the Mississippi, generally is regarded as the leading candidate for DOT endorsement, pending completion of a Justice Department study on the antitrust implications of merging Norfolk Southern's system with Conrail's 15-state, 15,000-mile operation.

The other bidders are Alleghany Corp., a New York holding company with a long history of railroad involvement, and a group of investors headed by Washington hotelier J.W. (Bill) Marriott Jr. All have offered about $1.2 billion for the railroad and have agreed to surrender Conrail's tax advantages and writeoffs. L. Stanley Crane, Conrail's chairman, has proposed a public offering that Conrail management says could raise $1.4 billion.

That leaves the question of how the bidders will settle with Conrail's employes, most of whom are unionized and have contributed to Conrail's financial comeback by accepting wages 12 percent below the industry standard, and by permitting considerable work-force reductions.

Labor officials have said they have reached agreement in principle with Alleghany and Marriott. They held talks with Norfolk Southern last week and have had preliminary discussions with Crane's representatives.

Conrail was created by the federal government in 1976 from the Penn Central and six other failing northeastern railroads. The federal government poured more than $7 billion into the operation before it turned the corner in 1982. It is expected to show a record profit of about $500 million for 1984.

The federal government owns 85 percent of Conrail's stock; the employes own 15 percent.